Re: Sorting two arrays with one call to sort()?

John <>
Sun, 23 Sep 2007 01:38:39 CST
On Sep 22, 3:12 pm, Ben Rudiak-Gould <> wrote:

John wrote:

I havetwoseparatearraysA and B. The comparison function only
depends on elements in A (keys are in A),
but the swap() function needs to swap not only A[i],A[j], but also
B[i],B[j] ; whenever it swaps A[i],A[j].
Can this be doneusinginternalsort() of C++?

I should hope so, since the main point of the STL is to decouple algorithms
from data structures. Something like this ought to work:

  struct double_iterator {

    T* const a; U* const b; size_t i;

    struct ref {
      T& p; U& q;
      ref(T& p, U& q) : p(p), q(q) {}

    ref operator*() { return ref(a[i], b[i]); }

    // ...


  inline void operator=(ref x, ref y) { x.p = y.p; x.q = y.q; }
  inline bool operator<(ref x, ref y) { return x.p < y.p; }

  // ...

  std::sort(double_iterator(A,B,0), double_iterator(A,B,size));

I think this will be as efficient as a hand-codedsortif you have a decent

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Here is as far as I got, it still doesnt work :(

#include <iostream>

using namespace std;
const int N = 10;

template < typename tA, typename tB >
struct double_iterator {
    tA* a;
    tB* b;
    size_t i;

    struct ref {
        tA& p; tB& q;
        ref(tA& p, tB& q) : p(p), q(q) {};
        void operator=(ref y){
      p= y.p; q = y.q;
        void operator<(ref y){
            return p < y.p;

    ref operator*(){ return ref(a[i],b[i]); }
    double_iterator(tA* _a, tB* _b, size_t _i){
        a = _a;
        b = _b;
        i = _i;

int main(void){
    int A[N];
    float B[N];

    for (int i = 0; i < N; ++i){
     A[i] = rand(); B[i] = A[i] % 10;
     cout << "\t" << A[i] << "\t" << B[i] << endl;


    for (int i = 0; i < N; ++i){
     cout << "\t" << A[i] << "\t" << B[i] << endl;

    return 0;

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